fix test failures as julia now returns substrings from string operations
fix test failures as julia now returns substrings from string operations

yuyichao/OpenCL.jl,yuyichao/OpenCL.jl,tkelman/OpenCL.jl,JuliaPackageMirrors/OpenCL.jl,JuliaPackageMirrors/OpenCL.jl,tkelman/OpenCL.jl